#include <bits/stdc++.h>
using namespace std;

int main(){
    double x1, y1, x2, y2, x3, y3;
    while(cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3){
        if(x1 == 0 && y1 == 0 &&
           x2 == 0 && y2 == 0 &&
           x3 == 0 && y3 == 0){
            break;
        }
        double s = (x2-x1)*(y3-y1) - (y2-y1)*(x3-x1);
        double ans = s / 2;
        cout << fixed << setprecision(6) << abs(ans) << endl;
    }
}